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Some stars may host multiple generations of planets, a dazzling new photo suggests. The newly released image, which was captured by the Very Large Telescope Interferometer (VLTI) in Chile, shows a dusty disk around an old double star called IRAS 08544-4431, which lies about 4,000 light-years from Earth in the southern constellation of Vela (The Sails). Scientists created this video look at the dust-shrouded star to showcase the discovery. This disk is very similar to the planet-forming structures commonly observed around young stars. While it's not clear whether planets actually do take shape around older stars, the new photo — the sharpest ever taken of such a disk around a mature star — hints that this is a possibility, researchers said. [The Strangest Alien Planets (Gallery)] "Our observations and modeling open a new window to study the physics of these disks, as well as stellar evolution in double stars," study co-author Hans Van Winckel, of the Instituut voor Sterrenkunde in Belgium, said in a statement. "For the first time, the complex interactions between close binary systems and their dusty environments can now be resolved in space and time." The scientists used several VLTI telescopes, an associated instrument called the Precision Integrated-Optics Near-infrared Imaging ExpeRiment (PIONIER) and a new high-speed infrared detector to take the photo. "We obtained an image of stunning sharpness — equivalent to what a telescope with a diameter of 150 meters [490 feet] would see," study team member Jacques Kluska, of Exeter University in England, said in the same statement. "The resolution is so high that, for comparison, we could determine the size and shape of a 1-euro coin seen from a distance of 2,000 kilometers [1,240 miles]." The IRAS 08544-4431 system consists of an old red giant star, as well a nearby, younger, "normal" star. The dust that comprises the newly imaged disk was expelled by the red giant, researchers said. "We were also surprised to find a fainter glow that is probably coming from a small accretion disk around the companion star," said study lead author Michael Hillen, also of the Instituut voor Sterrenkunde. "We knew the star was double, but weren't expecting to see the companion directly," Hillen added. "It is really thanks to the jump in performance now provided by the new detector in PIONIER, that we are able to view the very inner regions of this distant system." Hillen and his colleagues are publishing their results in the journal Astronomy & Astrophysics. The VLTI is located at the European Southern Observatory's Paranal Observatory in northern Chile. Follow Elizabeth Howell @howellspace, or Space.com @Spacedotcom. We're also on Facebook and Google+. Original article on Space.com. Copyright 2016 SPACE.com, a Purch company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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Site: phys.org

This star is surrounded by a disc of gas and dust—such discs are called protoplanetary discs as they are the early stages in the creation of planetary systems. This particular disc is seen nearly edge-on, and its appearance in visible light pictures has led to its being nicknamed the Flying Saucer. The astronomers used the Atacama Large Millimeter/submillimeter Array (ALMA) to observe the glow coming from carbon monoxide molecules in the 2MASS J16281370-2431391 disc. They were able to create very sharp images and found something strange—in some cases they saw a negative signal! Normally a negative signal is physically impossible, but in this case there is an explanation, which leads to a surprising conclusion. Lead author Stephane Guilloteau takes up the story: "This disc is not observed against a black and empty night sky. Instead it's seen in silhouette in front of the glow of the Rho Ophiuchi Nebula. This diffuse glow is too extended to be detected by ALMA, but the disc absorbs it. The resulting negative signal means that parts of the disc are colder than the background. The Earth is quite literally in the shadow of the Flying Saucer!" The team combined the ALMA measurements of the disc with observations of the background glow made with the IRAM 30-metre telescope in Spain. They derived a disc dust grain temperature of only -266 degrees Celsius (only 7 degrees above absolute zero, or 7 Kelvin) at a distance of about 15 billion kilometres from the central star. This is the first direct measurement of the temperature of large grains (with sizes of about one millimetre) in such objects. This temperature is much lower than the -258 to -253 degrees Celsius (15 to 20 Kelvin) that most current models predict. To resolve the discrepancy, the large dust grains must have different properties than those currently assumed, to allow them to cool down to such low temperatures. "To work out the impact of this discovery on disc structure, we have to find what plausible dust properties can result in such low temperatures. We have a few ideas—for example the temperature may depend on grain size, with the bigger grains cooler than the smaller ones. But it is too early to be sure," adds co-author Emmanuel di Folco (Laboratoire d'Astrophysique de Bordeaux). If these low dust temperatures are found to be a normal feature of protoplanetary discs this may have many consequences for understanding how they form and evolve. For example, different dust properties will affect what happens when these particles collide, and thus their role in providing the seeds for planet formation. Whether the required change in dust properties is significant or not in this respect cannot yet be assessed. Low dust temperatures can also have a major impact for the smaller dusty discs that are known to exist. If these discs are composed of mostly larger, but cooler, grains than is currently supposed, this would mean that these compact discs can be arbitrarily massive, so could still form giant planets comparatively close to the central star. Further observations are needed, but it seems that the cooler dust found by ALMA may have significant consequences for the understanding of protoplanetary discs. This research was presented in a paper entitled "The shadow of the Flying Saucer: A very low temperature for large dust grains", by S. Guilloteau et al., published in Astronomy & Astrophysics Letters.

News Article | April 16, 2016
Site: www.huffingtonpost.com

Astronomers say they've recently discovered an elusive dwarf galaxy orbiting our own Milky Way. There are about four dozen galaxies that we know of circling our own, New Scientist reported. Our newly named neighbor, Crater 2, is the fourth largest, according to a paper published in the Monthly Notices of the Royal Astronomical Society on Wednesday. (The biggest satellite galaxy of the Milky Way is the Large Magellanic Cloud, nearly 200,000 light years away.) Crater 2 sits some 400,000 light years away, said paper co-author Dr. Vasily Belokurov, an astrophysicist at the University of Cambridge's Institute of Astronomy.  "This is indeed a very rare discovery," Belokurov told The Huffington Post. "A galaxy like Crater 2 is a sort of invisible object." Researchers at Cambridge’s Institute of Astronomy discovered the dwarf galaxy in January when they used a computer algorithm to pinpoint where there might be a significant clustering of stars in images taken of space beyond our Milky Way. They identified a never-before-seen cluster of stars -- and concluded that this was evidence of a dwarf galaxy. Analysis of the data revealed that Crater 2 is roughly the same age as the universe, and its angular size is at least twice that of our own moon. "We have found many similar objects in the last 10 years, but never such a large beast," Belokurov said. "It is orders of magnitude less luminous compared to most objects of similar size. It is extremely diffuse. We believe it was born that fluffy. But why, we do not yet know." Dr. Jay Pasachoff, an astronomer at Williams College in Massachusetts, who was not involved in the new discovery, said that to find such a faint and diffuse galaxy is a nice piece of research. "It is always fun to discover a nearby neighbor about which we didn't know before, and the dwarf galaxy Crater 2 falls into that category," said the co-author of The Cosmos. "It seems to be aligned with a handful of other astronomically nearby objects, which may be teaching us how our group of galaxies formed." The same research team discovered a treasure trove of nine new dwarf galaxies orbiting our Milky Way last year. At the time, Dr. Sergey Koposov of Cambridge’s Institute of Astronomy, who led that previous study, said in a statement, "The discovery of so many satellites in such a small area of the sky was completely unexpected ... I could not believe my eyes." Until 10 years ago, only a dozen dwarf satellite galaxies had been identified around the Milky Way. But Belokurov said that he and his colleagues have since found several tens more. "In the last two years alone, the number of known Milky Way satellite galaxies has doubled, largely thanks to the Dark Energy Camera on the Blanco 4 meter telescope in Chile," Dr. Evan Kirby, assistant professor at Caltech Department of Astronomy & Astrophysics, who was not involved in the research, told HuffPost. "These galaxies are intense concentrations of dark matter," he added. "If there's a place in the universe where we can look to learn about dark matter, it's dwarf galaxies. How is it distributed? What is it made of?  Future observations, especially spectroscopy, will help answer those questions." Dwarf galaxies are the most numerous type of galaxy in the universe. "While we cannot say for sure this particular dwarf is the oldest in the universe, dwarf galaxies in general are," Belokurov said. "They are the first systems to be assembled, so they contain the information about the gas densities and the efficiencies of turning that gas into stars," he added. "As we have seen with the follow-up studies of similar objects, many stars in them look like the direct descendants of the very first stars in the universe."

The central map shows the distribution on the sky of the Boss Great Wall. The area subtended by this structure is the equivalent of 400 times the angular size of the Moon, and it is situated at more than 4 thousand million light years away from us.  On the map, each point represents a galaxy, while the colours represent the density of the surroundings. So the red areas correspond to the regions with the maximum concentration of galaxies. In the four RGB images from the SDSS (Sloan Digital Sky Survey), each red dot is a galaxy chosen for study, (surrounded by other galaxies at different distances). To show comparison, the combined angular size of these four detailed images is hardly one hundredth of the angular size of the Moon, very tiny compared to the angular size of the complete map. Credit: Alina Streblyanska (IAC). A group of researchers, among them scientists from the IAC, has discovered one of the most distant and massive "hyperclusters" of galaxies found thus far: the BOSS Great Wall (BGW). According to Heidi Lietzen, the principal investigator of this research, there is probably no other similar system so clearly isolated and with a comparable size. As this astrophysicist explains "superclusters of galaxies are the largest structures in the universe, formed by groups of galaxies bound together by their gravitational interactions. These huge structures, with sizes between 10 and 50 megaparsecs, (30 to 150 million light years) can host thousands of galaxies. Galaxies started to form in the early universe, in those regions where the density of matter was somewhat higher than average. Slowly, all the matter began joining and moving toward the denser zones, where the superclusters formed after a long process. They are young structures compared with other systems such as normal galaxy clusters, because it took millions of years for them to group together into a single system. In this way, the structure of the universe as a whole can be seen as the "cosmic web" predicted by Yakov Zeldovich, in which the material of the universe is organized within interconnected filaments around voids which have a much lower density. The results of the study, published today in the journal Astronomy & Astrophysics have shown the presence of the BGW system, with a diameter of some 900 million light years. It is formed by two superclusters and two "walls" of galaxies, probably bigger in volume and diameter than any other known hypercluster. The structure as a whole contains some 830 galaxies, which make it one of the most massive hyperclusters known. The Sloan Great Wall, the most similar known hypercluster of galaxies, which is 160 Mpc long, has about half the mass of the BGW. "To detect the BOSS Great Wall hypercluster measurements were made of 500,000 galaxies to reconstruct the space distribution of the luminous density. The BGW is clearly the biggest isolated structure in volume which has been studied in space," commented José Alberto Rubiño, one of the other authors of the study. The sample was taken from the Sloan Digital Sky Survey (SDSS), a project which has mapped and catalogued the universe to study it in depth. These enormous structures give us valuable information to compare with cosmological models. They can even challenge the numerical simulations that describe the formation and evolution of structures in the universe, because these simulations ought to be able to predict structures as big as this. The superclusters and hyperclusters are very useful for understanding how galaxies have evolved, because this evolution should be quicker in high density environments. "Studying hyperclusters can give us clues about how to predict just when and how matter groups together, and offers new challenges to existing cosmological models," says Alina Streblynanska, an astrophysicist at the IAC. More information: H. Lietzen et al. Discovery of a massive supercluster system at ~ 0.47 , Astronomy & Astrophysics (2016). DOI: 10.1051/0004-6361/201628261

News Article | April 7, 2016
Site: www.rdmag.com

What is the enigmatic planet nine like? Is it a super-Earth, or more like its cosmic neighbors, Uranus and Neptune? How big is it? What’s its temperature? The hypothetical planet is shrouded in mystery. However, that doesn’t stop inquisitive minds. The aforementioned questions have been pondered by University of Bern researchers Esther Linder and Christoph Mordasini since January, when researchers announced evidence of a ninth planet. Linder and Mordasini, in their study published in Astronomy & Astrophysics, operated under the assumption that planet nine would be a smaller version of Uranus and Neptune. With that in mind, they traced the thermodynamic evolution of such a planet since the solar system’s formation, around 4.6 billion years ago. The researchers said they believe the planet is around 700 astronomical units away. According to the University of Bern, the researchers concluded planet nine’s mass is equal to 10 Earth masses, has a radius that measure 3.7 Earth radii, and a temperature of 47 Kelvin (minus 226 Celsius). “This means that the planet’s emission is dominated by the cooling of its core, otherwise the temperature would only be 10 Kelvin,” said Linder in a statement. “Its intrinsic power is about 1,000 times bigger than its absorbed power.” The researchers’ planet nine model consisted of an iron core, which was wrapped in a silicate mantle followed by a water ice layer, and finally in a hydrogen and helium envelope. The researchers also attempted to figure out why planet nine has evaded human detection. “They calculated the brightness of smaller and bigger planets on various orbits,” according to University of Bern. “They conclude that the sky surveys performed in the past had only a small chance to detect an object with a mass of 20 Earth masses or less, especially if it is near the farthest point of its orbit around the sun.” However, a planet with a mass more than 50 Earth masses would be detectable by extant telescopes, such as NASA’s Wide-field Infrared Survey Explorer. Astronomers may be close to figuring out planet nine’s location. According to Universe Today, recent evidence shows that small perturbations in Cassini’s orbit around Saturn may be caused by the ninth planet.

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